I've done quite some reading and testing the last two days on this apparently well know problem. I've only I knew about this before I went on and bought a xonar dgx and logitech z506...
But so far I'm under the impression there isn't a whole lot you can do. The most useful tips I've come across where either wrap ur sound card in aluminium foil or buy new hardware all together. Not really satisfying. And since I think my problem is more specific I'm hoping someone on this site can give me better advice.
Xonar DGX, installed 3 slots below Radeon 7850, connected to a logitech z506 speakerset
No interference when sound card is connected to older 2.1 system ^^
when even the lightest 3D game is launched, like even worms!
5.1 speakerset connected to on board audio
When the graphics card is stressed to 99% with AIDA64 the humming is barely noticeable.
When done with OCCT where an actual visual texture is simulated the humming is identical to the one in games.
-I hadn't tried the xonar in a different slot since the only one available is on just above the hd7850. Just to be sure I did switch the card just now and the problem didn't get worse but just staid the same.
-I disabled spread spectrum and tried the drivers from brainbit without any success dow
The best results I have gotten so far is actually by settings the volume on the speakers it self as low as possible and then maxing the volume in game/audio-panel.
Could I conclude from this, since the 2.1 speaker set (also logitech btw) does not pick up any interference, that it might be the cabling from the logitech z506 who picks it up?